Server Error in '/' Application. [solved]

Hi,

We are getting an error on one of the items that we have, but this only appears in a test environment and not production, do you have any clue on what this error means?

It appears when we try and open the item in management centre, and we have checked that it has a table in the database:

Index and count must refer to a location within the string.
Parameter name: count

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ArgumentOutOfRangeException: Index and count must refer to a location within the string.
Parameter name: count

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[ArgumentOutOfRangeException: Index and count must refer to a location within the string.
Parameter name: count]
   System.String.Remove(Int32 startIndex, Int32 count) +5253145
   Dynamicweb.Admin.ItemTypeEdit._Lambda$__71(String path) +80
   Dynamicweb.Admin.ItemTypeEdit.FillIconSelectorControls(String selectedSmall, String selectedLarge) +784
   Dynamicweb.Admin.ItemTypeEdit.LoadData() +1009
   Dynamicweb.Admin.ItemTypeEdit.Page_Load(Object sender, EventArgs e) +112
   System.Web.UI.Control.OnLoad(EventArgs e) +95
   System.Web.UI.Control.LoadRecursive() +59
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +678

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.6.1055.0

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